First-Principles Study of NaFeAs, NaCoAs, and NaNiAs

To investigate the material dependence of the electronic structure of arsenide superconductors, the chemical trend of the Kohn-Sham band structures of a series of compounds, i.e., NaFeAs, NaCoAs, and NaNiAs, is studied by first-principles calculation based on generalized gradient approximation. Hypothetical structures of NaCoAs and NaNiAs in P4/nmm are found to be stable by structural optimization simulation. Results on the electronic states suggest that a characteristic two-dimensional electronic structure appearing as rodlike Fermi pockets is clearly found only in NaFeAs, while three-dimensional electronic structures are found in NaCoAs and NaNiAs with larger density of states than NaFeAs at the Fermi level, when paramagnetic electronic states are assumed.